When operating a physical camera in the physical world, a camera operator can see other physical objects (for example, people on a field) around the physical camera and choose to not collide with the physical objects. Further, the people on the field can see the physical camera and camera operator and choose to not collide with camera or operator. In a system where the camera operator is controlling a virtual camera, being a camera which exists virtually in a virtual reconstruction of physical world, the same affordances are not present.
The purpose of a virtual camera system is to capture camera footage simulating a physical camera but without the practical issues of having a physical camera in close proximity with objects in the real world. A physical camera can in some circumstances interfere with what is happening in a scene. The goal for a virtual camera system is to leverage the advantages of a virtual camera while keeping visual characteristics of a physical camera. For example, a virtual camera system may be able to fill the field of view with the object of interest if desired by the camera operator.
Virtual camera systems are usually associated with clipping planes, for example a near clipping plane and a far clipping plane. Clipping planes are typically orientated parallel to a virtual camera's image plane, and positioned close to the virtual camera for the near clipping plane and far in the distance for the far clipping plane. Clipping planes provide constraints onto the virtual camera's field of view and define where polygons of an object mesh become visible to, and rendered by, the virtual camera. The distance of the near clipping plane is set to both allow the object to approach the virtual camera while not causing the object to appear massively distorted. In practice, it is difficult to for the camera operator to know this distance and keep the object of interest just in front of the near clipping plane. Often, the object in the virtual camera view collides with a near clipping plane and the mesh of the object is sliced as the object is passed through the clipping plane. The virtual camera resultantly renders only a portion of the mesh of the object while also rendering a portion of the interior of the object mesh. Collision of an object with a clipping plane is an undesirable result especially if the virtual camera system is intended to produce realistic camera footage.
People in the physical world are not able to sense the position of the virtual camera, and as a result can freely collide with virtual cameras. The same is true for the camera operator controlling the virtual camera. The camera operator, likely controlling the virtual camera via a monitor screen will have a reduced level of context awareness and won't be able to sense objects around the virtual camera. The lack of context awareness of means that objects can pass through the virtual camera from behind. The objects are initially out of view of the camera operator, and instantly fill the virtual camera's field of view as the objects pass the virtual camera's near clipping plane. The objects instantly filling the virtual camera view cause an interruption when trying to compose an object in the field of view of the virtual camera.
A need exists to address virtual objects visibly being clipped by the clipping plane. A need also exists to propose a method reducing disruptive occlusions caused by objects suddenly moving appearing in frame close to a virtual camera.
The video game industry has experienced similar problems, and has developed standard methods to address the problems described above. One known method implements a collision radius around objects ensuring that the objects do not collide with each other in the first place. Using a collision radius results in the camera bouncing off objects as they collide with the camera; undesirably adjusting the camera operator's composition. Another known method fades out an object when the object passes a distance threshold around the camera. The method treats all objects equally so objects passing through the camera from in front of the camera will fade out over the same distance as objects passing through the camera from behind